Epigenetic modifications are heritable changes to gene expression without
physical changes to the actual DNA sequence. The most widely studied epigenetic
modification is DNA methylation, as it is influenced by aging, diet, diseases and the
environment. DNA methylation involves direct chemical modification to the DNA and
plays an important role in gene regulation by preventing proteins from binding to
certain regions of the DNA, which causes these regions to be repressed. It is essential
for normal development, cell differentiation and regulation of cellular biology. The
DNA methylation landscape of each unique cell type helps to determine which genes
are expressed and silenced. It is well known today that the accumulation of both
genetic and epigenetic abnormalities contributes to the development of cancers.
Aberrant DNA methylation is a hallmark of cancer. During cancer development and
progression, the methylation landscape undergoes aberrant remodelling. Recently
within cancer research, the advancements in DNA methylation mapping technologies
have enabled methylation landscapes to be studied in greater detail, sparking new
interest in how the methylation landscape undergoes a change in cancer and possible
applications of DNA methylation. This chapter focuses on reviewing DNA methylation
landscapes in normal cells and then how they are altered in cancer. It also discusses the
applications of DNA methylation as cancer biomarkers.
Keywords: Biomarkers, Cancer, Demethylation, DNA, Epigenetics, Gene-bodies, Gene expression, Hypermethylation, Hypomethylation, Methylation, Promoter, Transcription.